1. Technical Field
This application relates to UMTS (Universal Mobile Telecommunications System) in general, and to an apparatus and method for operating a communications device in a mobile communications network.
2. Description of the Related Art
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In a typical cellular radio system, mobile user equipment (UE) communicates via a radio access radio network (RAN) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
UMTS is a third generation public land mobile telecommunication system. Various standardization bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
Reference is also directed to 3GPP TSG—Services and System Aspects “Vocabulary for 3GPP Specifications (Release 1999)” 3GPP TS 21.905 v3.2.0 which defines terminology used in this document.
Consider a wireless mobile device, generally referred to as user equipment (UE), that complies with the 3GPP specifications for the UMTS protocol. The 3GPP 25.331 specification, v.3.15.0, referred to herein as the 25.331 specification, addresses the subject of UMTS RRC (Radio Resource Control) protocol requirements between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE. The 3GPP 25.322 specification, v3.15.0, referred to herein as the 25.322 specification, addresses the subject of UMTS RLC (Radio Link Control) protocol requirements between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE.
In accordance with clause 9.7.3 of the 25.322 specification, the RLC layer of the 3G UMTS stack may, in certain circumstances, discard an SDU (Service Data Unit). There are thus proposed strategies for handling the discard of an SDU. A number of such strategies are detailed below.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of an apparatus and method for operating a communications device in a mobile communications network.
The same reference numerals are used in different figures to denote similar elements.